The GRUB menu appears, Ubuntu starts — but there is no Windows line to choose. Windows itself is unharmed and a keypress away through the firmware menu. What is missing is one menu entry, and the reason is a GRUB default that surprises everyone the first time.
GRUB builds its menu by scanning for other operating systems with a helper called os-prober. Since GRUB 2.06 — the version Ubuntu 22.04 arrived with — os-prober is switched off by default when GRUB updates its configuration, for security reasons. Installations done the automatic alongside way usually still get their Windows entry from the installer itself, but a manual install, a GRUB reinstall or a later configuration update can leave the menu with Ubuntu only. The fix is one line and one command.
Before changing any configuration, prove the patient is alive. Nothing in this fix matters if Windows itself is gone, and it almost never is.
lsblk -f and look for your Windows NTFS partition in the listWindows present in both checks means the situation is exactly the title of this page — a missing menu entry, not a missing system. That is the good outcome, and the rest is configuration.
It helps to know this is deliberate, not a bug in your install. Scanning other systems' boot files and trusting what it finds was judged a security risk, so GRUB's makers disabled the scan by default and left a switch for people who genuinely dual boot.
update-grub run without the switch keeps the menu Ubuntu-onlySo the fix is not to hack the menu by hand. It is to flip GRUB's own switch back on, once, and let the tool rebuild the menu the proper way.
Three moves in a terminal: open the GRUB settings file, add the switch, regenerate.
sudo nano /etc/default/grubGRUB_DISABLE_OS_PROBER=false — the name reads backwards, but false here means os-prober is allowed to runsudo update-grub and watch the outputThe line you are hoping to see scroll past is in the panel below — GRUB announcing that it found Windows Boot Manager. When it appears, restart and the Windows entry is sitting in the menu.
If os-prober is enabled and the Found line never appears, the scan ran but found nothing it trusted. The causes narrow quickly from there.
lsblk output and mounts without errorWork them in that order. Mode mismatch is the most common of the three by far, and it is also the one no amount of update-grub runs can fix from inside Ubuntu.
Once the switch is set, later configuration updates keep using it — the Windows entry survives ordinary updates. What can still remove it is a fresh GRUB reinstall or a repair tool writing a new default configuration.
/etc/default/grub and confirm the os-prober line survivedDual boot menus are machinery, and machinery likes a little attention. One enabled switch turns this particular failure into a thirty-second non-event forever.
Watch the complete dual boot installation and menu setup from the video, done live from ISO to GRUB.
▶️ Watch Full VideoBecause the menu and the system are separate things. GRUB stopped scanning for other systems by default — os-prober is disabled in current GRUB versions — so a rebuilt configuration contains only Ubuntu. Windows was never touched, which the firmware boot menu proves in one start. Enabling os-prober and running update-grub restores the entry.
It reverses a deliberate default, so be aware of the trade: GRUB will scan attached systems' boot files when building its menu. On your own home machine with your own Windows install, that is the normal dual boot arrangement millions of people run. On a machine exposed to untrusted drives, the default exists for a reason — the choice is yours and it is documented here honestly.
Then the scan found nothing usable. The usual reasons are a boot mode mismatch — Ubuntu in legacy mode cannot add a UEFI Windows — an EFI partition that is not mounting, or damaged Windows boot files. Confirm Windows still starts from the firmware boot menu; that single test splits the causes in half.